Dewaxing solvent and solvent recovery



0d 6, 1942. J. v. MONTGOMERY erm. 2,297,839

DEWAXING SOLVENT AND SOIVENT RECOVERY Filed Sept. 25, 1940 Patented Oct. 6, 1942 UNITED STATE s PATENT orellcaI DWAXING SOLVENT AND SLVENT aacovaar v Y James V. Montgomery, Okmulgee, and Robert W.

" Henry, Bartlesville, Okla.,

ssamm to mumps Petroleum Company,a corporation of Delaware Application September 25, 1940, Serial No. 358,342

owns.

This invention relates to mineral oil refining, and more particularly it relates to an improved dewaxing solvent and method of preparing 'said' improved solvent for continued reuse.

It is known to use unsaturated heterocyclic nitrogen bases such as pyridine, picolines, etc., as dewaxing solvents in the reiiningof mineral oils.

Picolines` are very effective dewaxing solvents naphtha hydrocarbons of suitable boiling point,

the-lower ethers such as isopropyl, propyl, ethyl, methyl-ethyl, methyl-propyl, etc., and thioethers of suitable boiling points may be used advantageously' with picolines for dewaxing. Furthermore, a process is-presented in which any of these be withdrawn from the dewaxing system` and dried. The removal of small quantities of water from a material in which'water is very soluble, such as picolines, is frequently an expensive and none too efficient and satisfactory anoperation.

An object of this invention is .to prepare an improved solvent for dewaxing of lubricating or other oils.

Another object of this invention is to prepare a dewaxing solvent which will be useful even in the presence of small quantities of dissolved water. i a

Still another object of this invention is to furnish a satisfactory and economic method for the removal Aof quantities of interfering water 'from such dewaxing solvents as picolines.

Still other objects and advantages will be apparent from a study of the following disclosure.

We have discovered a dewaxing process involving a method for the convenient and efficient 'use of picolines or picoline mixtures with other organic solvents and the like. We propose to mix with the picolines certain compounds which increase the solubility of the oil in the solvent mix` ture, or in other words decreases the miscibility temperature of the oil and solvent to overcome the reverse effects caused by the presence of small quantities of water which accumulate in the solvent; and thereby increase the tolerance of the picolines fo'r water in dewaxing operations. I'he added material also assists in removing the small quantities of accumulated water from the solvent system, as will be disclosed below.

To satisfy these conditions the added material should have the following characteristics: (l) A lower miscibility temperaturewith the waxy oil than picolines alone; (2) Complete miscibility with picolines; (3) Relative immiscibility with water; and (4) A boiling point below approximately 200 -F. We have found that benzene,

added. materials may be used as an aid in removing contaminating water from the dewaxing solvent.

The figure illustrates one form of apparatus and one method for carrying out our invention.

Referring to the' ligure, thev oil-solvent mixture, as for example the oil-picoline mixture, or

the wax-solvent mixture containing frozen moisture or water from the wax filters passes through line I into heater 2 in which the mixture is heated to stripping still temperatures. The heated mixture passes from heater 2 through line I into stripping still l in which the dewaxing solvent mixture is stripped from the dewaxed oil or wax. Solvent vapors from this stripping still pass overhead through line 5 into condenser 6 in which they are condensed or partly condensed.

thenc'evthrough line 1 and into fractionating tower 8. In fractionator 8 the partially condensed solventl vapors are reboiled suillciently to remove any water present as vapors of a constant boiling mixture of picolines and water along with vapors of the low boiling added material such as benzene. Water-free, dry picolines exit from fractionator 8 through lines Il and I5 to run or intermediate storage, not shown. Heat for this reboiling is furnished by passage of the solvent-free dewaxed oil or wax from bottom of stripper 4 'through line 30 and into closed reboiler coils 31. From the reboiler coils 31, the stripped oil passes through line 38 to stripped dewaxed oil storage or stripped wax, not shown.

The mixed vapors, that is picoline-water-constant boiling mixture vapors and benzene vapors pass over head from said fractionator through line 9, are condensed and cooled in condenser I0, pass through lines II and 33 into separator I2. Since water is relatively insoluble in liquid benzene, upon condensation of the mixed vapors in I0, two phases separate. These two phases are permitted to settle in separator I2. The upper phase I3 contains the benzene with dissolved Plcolines, while the lower phase 30 is awater solu- Ytion of picolines. These two phases separate because of the mutual insolubility of water and benzene: Since picolines are soluble in water and in benzene, layers containing these latter substances dissolve picolines according to the distribution or partition phenomenon. A portion of the upper phase. that is benzene and picolines, is transferred by pump 34 through line 35 to re- .iiux fractionator 8. The remainder of the ben zene-picoline solution leaves the top f theseparator I2 through line I6 and joins the dry picolines coming from the bottom of fractionator I through line I4, and the combined stream oi.' dry dewaxing solvent passesthrough line i5 to run storage, not shown, preparatory to reuse.

The lower or picoline-water layer 39 from separator l2 passes through line i1 toi run storage i8, from which said water-picoline solution 1s transferred by pump i9 through line 20 into heating coil 2|, thence through line 22 and into fractionator 23. Vapors from the top of this fractionator 23 consist of a constant boiling mixture of picolines and water and are conducted through overhead line 24 into condenser and cooler 25, and the condensed kconstant boiling mixture is accumulated in receiver 26- A pOltOn of this water-picoline solution is transferred by pump 21 through line 28 to reilux tower 23, while the remainder of said solution leaves accumulator 26 by Way of line 30, pump 3|, line 32, and joins the liquid in line II`. This combined stream of water-benzene-picolines from line il and waterpicolines from line 32 enters separator I2 through line 33. c l

Essentially picoline-free water is removed from the bottom of tower 23 through line 29. In this above-described manner, the dewaxing solvent is continuously freed of contaminating water by the solvent extraction of picolines from the water-picoline mixture by the benzene to form an essentially dry benzene-picoline solution.

The remaining water carries some picolines in 'solution and these latter are concentrated and yrecovered as a. constant boiling mixture and returned to the system while the water not consumed in forming this constant boiling mixture is withdrawn vas essentially picoline-free and benzene-free water.

To those skilled in the art it is obvious that excess drying-miscibility agent, above that desired for miscibility enhancing alone, may be fractionated from 'the dry solvent mixture before the latters return to the dewaxng step, the excess being kept recycling in the drying stage.

Though described as particularly adaptable to picolines, we do not wish to be limited by this application since the process may be used equally well with picoline mixtures, pyridine, lutidines,

collidines, and their alkyl derivatives, or mixtures of all. f Similarly, benzene has been used throughout our disclosure as the added agent for increasing the tolerance of the picoline 4solvent for water. l and as the water removing agent, but we do not,

desire to be limited to this one material since naphtha hydrocarbons of suitable boiling point, such ethers as iso-propyl, propyl, ethyl, methylethyl, methyl-propyl, etc., and many thin-ethers function equally well.

Likewise, our disclosure describes one methodl of carrying out our invention, but since various modifications of our disclosed ow chart may' be vadded an agent which has complete miscibility with the solvent, is relatively immiscible with f water and boiling below 200 F., which comprises heating the mixture and passing the same to a iirst recovery zone, the mineral oil being recovered from the bottom of the rst recovery zone and the solvent plus agent andwater recovered from the top of the said rst recovery zone as a vapor, condensing said vapor and passing the condensate to a second recovery'zone, heating said condensate in the second recovery zone, recovering frorn the bottom thereof a large proportion of the solvent as dry picoline and the vapors passing overhead being condensecland separated into two phases of picoline plus agent and picoline plus water in a third zone, removing the picoline plus agent phase and combining same with the large proportion of dry picoline from the second recovery zone as dried recycle dewaxing solvent, passing the picoline plus water phase to a fourth recovery zone to remove the excess water as bottoms and returning the picoline as a constant boiling point mixture with water therefrom to the third recovery zone.

2. ri'he continuous process of recovering solvent rrone as a vapor, condensing said vapor and passing the condensate to a. second recovery zone, heating said condensate in the second recovery zone, recovering from the bottom thereof a large proportion of the solvent as dry picoline and the vapors passing overhead being condensed and separated into two phases of picoline plus benzene and picoline plus water in a third zone, removing the picoline plus benzene phase and combining same with the large proportion of dry picoline from the second recovery zone as dried recycle dewaxing solvent, passing the picoline plus water phase to a fourth recovery zone to remove the excess water as bottoms and returning the picolineV as a constant boiling point mixture with water therefrom to the third recovery zone.

3. The continuous process ofl recovering solvent froml a dewaxed mineral oil which mineral oil contains traces of water and said water and solvent being mutually soluble, said solvent being an unsaturated heterocyclic nitrogen base to which has been added an agent which has come plete miscibility with the solvent, is relatively immiscible with water and boiling below 200 F., which comprises heating the mixture and passing the same to a first recovery zone, the mineral oil being recovered from the bottom of the made by those skilled in the art without departing from the spirit of our invention, we do not wish to be limited by the onedisclosed example.

We claim: 1. The continuous process of' recovering sol- -vent from a dewaxed mineral oil which mineral oil contains traces of water and said water and solvent being mutually soluble and forming a constant boiling point mixture boiling at a temfirst recovery zone and the solvent plus agent and water recovered from the top of the said rst recovery zone as a vapor, condensing said vapor and passing theA condensate to a second recovery zone, heating said condensate in the second re'- covery zone, recovering fromv the bottom thereof a large proportion of the solvent as dry heterocyclic nitrogen base and the vapors passing overhead being condensed and separated into two phases of' heterocyclic nitrogen base plus agent .and heterocyclic nitrogen base plusfwater in a third zone, removing the heterocyclic nitrogen base plus agent and combining same with the large proportion of dry heterocyclic nitrogen base ,y from the secondrecovery zone as a dried recycle dewaxing solvent, passing the heterocyclic nitrogen base plus waterphase' to a fourth recovery zone to remove the excess water as bottoms, and returning the heterocyclic nitrogen base as a constant boiling mixture with water therefrom to the third recovery zone.

4. 'I'he continuous process of recovering solvent from a dewaxed mineral oil which mineral* oil contains traces of water land said-water and solvent beingv mutually soluble and forming a constant boiling point mixture boiling at a temperature below that of water and of thesolvent, said solvent being a picoline mixture to which has been added an agent such as benzene, which comprises heating the mixture and passing the same to a ilrst recovery zone, the minerai oil beplus water phase to a fourth recovery zone to remove the excess water as bottoms and returningthe picoline mixture as a constant boiling point mixture with water therefrom to the third recovery zone.

5. The continuous process of recovering solvent from a dewaxed mineral oil which mineral oil contains traces 4of water and said water and solvent are mutually soluble, said solvent being apicoline mixture tovwhich has been added an l agent which has complete miscibility with the solvent, is relatively immiscible with water and boiling below 200 F., said agent being a petra-*5 leum hydrocarbon fraction boiling below 200 FJ, which comprises heating the mixture and passing the same to a rst recovery zone, the mineral oil Vbeing recovered from the bottom of the flrst rejcovery zone and the solvent plus agent and water recovered from the top of said iirst recovery zone ing recovered'from the bottoms of the first recovery zone and the solvent plus benzene and water recovered from the top of the said rst recovery zone'. as a vapor, condensing said vapor and passing the condensate to a second 'recovery zone, heating said condensate in the second'recovery zone, recovering from the bottom thereof p.- large proportion of the solvent as a picoline mixture and the vapors passing overhead being condensed and separated into two phases of picoline mixture plus benzene. and picoline mixture plus water in a third zone, removing the picoline mixture plusy benzene phase and combining same with the large proportion of dry picoline mixture from the second recovery zone as dried recycle dewaxing solvent, passing the picoline mixture phase from said third zone, passing the water plus picoline` mixture phase to a fourth recovery zone to remove the excess water and returning the remainder of the water plus picoline mixture as a constant boiling mixture from the fourth recovery zone to the third recovery zone.

JAMES v. MONTGOMERY. ROBERT W.l HENRY. 

